Method for agglomerating dispersed rubber

ABSTRACT

A process for the agglomeration of at least one rubber (A), dispersed in an aqueous phase, by the addition of a dispersion of at least one agglomerating polymer (B) in aqueous phase, in which the agglomerating polymer B used is one containing substantially no free acid groups and the agglomeration is carried out in the presence of at least one basic electrolyte.

The invention relates to a process for the agglomeration of at least onerubber (A), dispersed in an aqueous phase, by the addition of an aqueousdispersion of at least one agglomerating polymer (B).

Methods of enlarging rubber particles are known to the person skilled inthe art. One variant comprises agglomeration effected duringpolymerization of the rubber-forming monomers. Another method comprisesthe agglomeration of the substantially fully polymerized dispersedrubber. In the latter process there is also the problem that thedispersion, in addition to the desired agglomeration, forms coagulum(unstable, being over-large agglomerate). The coagulum impairs themechanical properties of the end product. Furthermore, coagulationreduces the yield of product. High yields are particularly important,especially in the case of plants operated on a large scale. In addition,when coagulum forms, the plant must be cleaned more often. Thus it isalways desirable to minimize coagulation.

In EP-A 77038 describes the agglomeration of a dispersed rubber in thepresence of a dispersion of an acid-group-containing agglomerating latexand in the presence of a neutral electrolyte. Since the agglomeratinglatex contains free acid groups, the agglomeration must be carried outat a pH of higher than 7, in order to dissociate the acid. This processsuffers from the drawback that, owing to the free acid groups in thelatex, the efficiency of the agglomeration is strongly influenced by pHfluctuations. The pH must thus be tuned very finely in order to obtainreproducible results. This is feasible in large-scale production plantsonly at high expense. The chlorides proposed as neutral electrolytessuffer from the further drawback that they corrode the reaction vesselsand pollute the wastewater, and even residues of these salts lead tocorrosion problems during processing. It was also known from EP-A 517539 that rubbers can be agglomerated with emulsion polymers containingat least 30% of units containing carboxylic acid groups. U.S. Pat. No.3,049,501 discloses an agglomeration method in which polyvinyl methylether containing acid groups is used at a pH from 8 to 11. GB-A 859 361proposes an agglomerating latex free from acid groups, together with anammonium salt electrolyte.

The processes proposed in these publications do not adequately preventthe formation of coagulum. Moreover, the use of volatile electrolytesmay lead to problems such as foaming of the reaction mixture.

Agglomerating latices exhibiting no free acid groups and capable ofcausing agglomeration intrinsically, i.e., independently of whether thepH is above 7 during agglomeration or not, have been disclosed in H.-G.Keppler, H. Wesslau, J. Stabenow, Angew. Makromol. Chem. 2 (1968) pages1 to 25.

It is an object of the invention to find a process by means of whichdispersed rubber particles can be efficiently agglomerated, especiallyin large-scale production, with the formation of coagulum minimized.

Accordingly we have found a process for the agglomeration of at leastone rubber (A), dispersed in an aqueous phase, by the addition of adispersion of at least one agglomerating polymer (B) in aqueous phase,in which an agglomerating polymer containing substantially no free acidgroups is used and in which the agglomeration is carried out in thepresence of at least one basic electrolyte. We have also found graftpolymers (C) obtainable from said agglomerated rubbers. We have alsofound thermoplastic molding compositions (D) which comprise said graftpolymers C and can be used for the preparation of shaped articles, filmsor fibers.

The rubbers A underlying the process of the invention can bemultifarious. For example silicone rubbers, olefin rubbers, such asethylene, propylene, ethylene/propylene, EPDM, diene, acrylate,ethylene-vinyl acetate rubbers or ethylene-butyl acrylate rubbers ormixtures of two or more of these rubbers can be used. Preferably,however, diene rubbers are used. Special preference is given as A todiene rubbers composed of

a1) from 50 to 100% by weight of at least one diene having conjugateddouble bonds and

a2) from 0 to 50% by weight of one or more other monoethylenicallyunsaturated monomers,

the sum of the percentages by weight being 100.

Suitable dienes having conjugated double bonds, a1), are, in particular,butadiene, isoprene and the halogen-substituted derivatives thereof,e.g., chloroprene. Preference is given to butadiene or isoprene,particularly butadiene.

The other monoethylenically unsaturated monomers a2) which may bepresent in diene rubber A at the expense of monomers a1) may be, forexample:

vinylaromatic monomers such as styrene and styrene derivatives of thegeneral formula

 in which R¹ and R² independently stand for hydrogen or C₁-C₈ alkyl;

acrylonitrile, methacrylonitrile;

C₁-C₄-alkyl esters of methacrylic acid or acrylic acid such as methylmethacrylate, and also the glycidyl esters glycidyl acrylate andmethacrylate;

N-substituted maleimides such as N-methyl-, N-phenyl- andN-cyclohexylmaleimides;

acrylic acid, methacrylic acid, and dicarboxylic acids such as maleicacid, fumaric acid and itaconic acid and also their acid anhydrides suchas maleic anhydride;

nitrogen-functional monomers such as dimethylaminoethyl acrylate,diethylaminoethyl acrylate, vinylimidazole, vinylpyrrolidone,vinylcaprolactam, vinylcarbazole, vinylaniline, acrylamide andmethacrylamide;

aromatic and araliphatic esters of acrylic acid and methacrylic acidsuch as phenyl acrylate, phenyl methacrylate, benzyl acrylate, benzylmethacrylate, 2-phenylethyl acrylate, 2-phenylethyl methacrylate,2-phenoxyethyl acrylate and 2-phenoxyethyl methacrylate;

unsaturated ethers such as vinyl methyl ether,

and mixtures of these monomers.

Preferred monomers a2) are styrene, acrylonitrile, methyl methacrylate,glycidyl acrylate and methacrylate or butyl acrylate.

Generally, diene rubbers A exhibit a glass transition temperature Tg ofless than 0° C. (determined as specified in DIN 53765).

The synthesis of rubbers A is known to the person skilled in the art ormay be carried out by methods known to the person skilled in the art.Thus diene rubbers A can be prepared in a first step in which they arenot formed in a particulate state, for example via solutionpolymerization or gas-phase polymerization, and are then dispersed inthe aqueous phase in a second step (secondary emulsification).

Heterogenous, particle-forming polymerization processes are preferredfor the synthesis of rubbers A. Dispersion polymerization can be carriedout in known manner by, say, the emulsion, inverse emulsion,miniemulsion, microemulsion, or microsuspension polymerization method.

Dispersion polymerization can be carried out in an organic solvent or anaqueous phase.

The rubbers A are preferably prepared in aqueous phase. By aqueous phaseis meant a solution, emulsion or suspension of the correspondingmonomers or polymers in water or in a solvent mixture containing a largeproportion, i.e., at least 20% by weight, of water.

In one preferred embodiment, polymerization is carried out by theemulsion method, in which the monomers are polymerized in aqueousemulsion at from 20 to 100° C., preferably at from 50 to 80° C., inwhich case all components of the batch can be combined (batch process),or the monomer alone or an emulsion of monomer, water and emulsifierscan be gradually added to the other components (feed process).Furthermore, it is possible to carry out the reaction by a continuousmethod. Preference is given to the feed process.

Suitable emulsifiers are for example alkali metal salts of alkyl- oralkylaryl-sulfonic acids, alkyl sulfates, fatty alcohol sulfonates,salts of higher fatty acids containing from 10 to 30 carbons,sulfosuccinates, ether sulfonates or resin soaps. Preferably, use ismade of the alkali metal salts of alkylsulfonates or fatty acidscontaining from 10 to 18 carbons. Their concentration is usually from0.5 to 5% by weight, based on monomers a) (sum of monomers a1 and a2).

Preferably, the preparation of the dispersion is carried out usingsufficient water to give the final dispersion a solids content of from20 to 50% by weight.

Free-radical initiators suitable for starting the polymerizationreaction are all those which decompose at the reaction temperaturechosen, i.e. both those which undergo decomposition thermally and thosewhich do so in the presence of a redox system. Suitable polymerizationinitiators are preferably free-radical initiators, for example peroxidessuch as preferably peroxodisulfates (e.g. sodium or potassiumpersulfate) or azo compounds such as azodiisobutyronitrile. However,redox systems, particularly those based on hydroperoxides such as cumenehydroperoxide, may alternatively be used.

Usually the polymerization initiators are used in a concentration offrom 0.1 to 2% by weight, based on monomers a).

The free-radical initiators and the emulsifiers are for example placedin the reaction vessel as a single batch at the start of the reaction inbatchwise mode, or are divided into a number of portions which are addedbatchwise at the start and at one or more intervals thereafter, or areadded continuously over a specific period. This continuous addition mayfollow a gradient, which may, for example, be ascending or descending,linear or exponential, or stepped (step function).

Use may also be made of molecular weight regulators such as ethylhexylthioglycolate, n- or tert-dodecyl mercaptan or other mercaptans,terpinols and dimeric α-methylstyrene or other compounds suitable formolecular weight regulation. The molecular weight regulators are addedto the reaction batch batchwise or continuously as described above withreference to the free-radical initiators and emulsifiers.

The pH at which polymerization is carried out is influenced by the typeof emulsifiers used. Polymerization is generally carried out at a pH ofpreferably from 6 to 10. Buffering agents such as Na₂HPO₄/NaH₂PO₄,sodium pyrophosphate, sodium hydrogencarbonate or buffers based oncitric acid/citrate may also be used. Regulators and buffering agentsare used in conventional amounts, so that more detailed informationthereon is unnecessary here.

The diene rubbers preferably used as A may, in a special embodiment, beproduced by polymerization of monomers a) in the presence of a finelydivided latex (“seed latex method” of polymerization). This latex isused as the initial batch and can consist of monomers capable of formingrubber-elastic polymers, or alternatively of other monomers such asthose mentioned above. Suitable seed latices consist for example ofpolybutadiene or polystyrene.

In one preferred embodiment of the emulsion polymerization the dienerubbers A can be produced by the feed process. In this process aspecific fraction of monomers a) is used as initial batch andpolymerization is initiated, after which the remainder of the monomersa) (feed fraction) is added as a feed stream during polymerization. Thefeed parameters (gradient shape, rate, duration, etc.) are governed bythe other polymerization conditions. The same applies here, by analogy,as stated above with reference to the manner of adding free-radicalinitiator or emulsifier. In said feed process the fraction of monomersa) used as initial batch is preferably from 5 to 50% by weight and morepreferably from 8 to 40% by weight based on a). Preferably, the feedfraction of a) is fed in over a period of from 1 to 18 hours, morepreferably from 2 to 16 hours and most preferably from 4 to 12 hours.

Inverse emulsion polymerization differs from emulsion polymerization inthat instead of hydrophobic monomers dispersed in an aqueous phase, useis made of hydrophilic monomers dispersed in a substantially nonaqueousphase.

Miniemulsion polymerization differs from emulsion polymerizationprimarily in that the mixture of monomers, water, emulsifiers andco-emulsifiers is subjected, in a first step, to high shearing forcesand the polymerization reaction is carried out in a second step. Thisproduces very fine monomer droplets. The batch is then polymerized bymeans of a water-soluble initiator, e.g., a persulfate. The particlesize distribution of the monomer droplets usually substantiallycorresponds to the later particle size distribution of the polymerparticles. The high shearing forces can be produced for example byultrasound or a microfluidizer appliance, or alternatively byhomogenizers. Details of the miniemulsion polymerization process may befound by the person skilled in the art in, say, P. Lovell, M. El-Aasser,Emulsion Polymerization and Emulsion Polymers, John Wiley, New York,1997, pp. 699-722.

In microemulsion polymerization very large amounts of emulsifier areused, thereby distinguishing it from emulsion polymerization. In thisway similarly large monomer droplets are produced as in miniemulsionpolymerization, but in the case of microemulsion polymerization thedroplets are thermodynamically stable.

In other respects the above statements concerning normal emulsionpolymerization apply to both miniemulsion and microemulsionpolymerization.

In microsuspension polymerization, a finely divided monomer emulsion isgenerally produced in a first step by the action of high shearingforces. For this purpose use is made of homogenizers, which are wellknown to the person skilled in the art. But compared with miniemulsionpolymerization, the droplets obtained are larger. Further, there areused, in microsuspension polymerization, at least one emulsifier and atleast one protective colloid.

The protective colloids suitable for stabilization of the dispersionduring polymerization by the microsuspension polymerization process arewater-soluble polymers, for example cellulose derivatives such ascarboxymethyl cellulose and hydroxymethyl cellulose,poly(N-vinylpyrrolidone), poly(vinyl alcohol) and poly(ethylene oxide),anionic polymers such as polyacrylic acid and their copolymers, andcationic polymers such as poly(N-vinylimidazole). The concentration ofthese protective colloids is preferably from 0.1 to 10% by weight, basedon the total mass of the dispersion.

Preference is given to the use of one or more polyvinyl alcohols asprotective colloids, particularly those having a degree of hydrolysisbelow 96 mol %, preferably from 60 to 94 and more preferably from 65 to92 mol %. The preferred polyvinyl alcohols have a dynamic viscosity offrom 2 to 100 mPas, preferably from 4 to 60 mPas, measured on a 4% byweight strength solution in water at 20° C. according to DIN 53015.

The microsuspension polymerization is initiated using a free-radicalpolymerization initiator. Such compounds are known to the person skilledin the art. In particular, the initiators used are organic peroxidessuch as dilauryl peroxide or azo compounds such as2,2′-azobis(2-methylbutyronitrile) or 2,2′-azobis(isobutyronitrile).Also used as free-radical polymerization initiators are monomers whichspontaneously polymerize at elevated temperature.

The concentration of the initiator is usually from 0.05 to 4% by weight,based on the monomers.

Further additives such as buffering agents and molecular weightregulators can be added continuously or batchwise at the start of and/orduring the preparation of the monomer dispersion and/or duringpolymerization.

The monomer dispersion is usually prepared at room temperature, buthigher or lower temperatures may be sensible depending on the type ofmonomers and protective colloids used.

Preparation of the monomer dispersion may be effected batchwise orcontinuously. Alternatively, it is possible to disperse the componentsin a first step as a batch and then to subject the resulting dispersionto a second dispersing operation carried out continuously.

Polymerization is carried out in conventional manner, for example byheating the reactor contents, by which means the polymerization reactionis initiated, or, in the case of a redox initiator, by bringing theinitiator into contact with the reducing agent. The polymerizationtemperature is governed, inter alia, by the monomers and initiatorsused, and also by the desired degree of crosslinking of the resultingpolymers A). Generally, polymerization is carried out at from 30 to 120°C., and if desired various temperatures can be used successively, or atemperature gradient can be employed.

The polymerization reaction is usually carried out with slow or gentleagitation, during which (unlike in the case of the precedingemulsification involving high shearing forces) the droplets are notbroken up further.

The particle size can thus be controlled, as already mentioned abovewith respect to the miniemulsion and microsuspension polymerizationmethods, substantially by appropriately selecting and regulating theconditions used during preparation of the dispersion (e.g., choice ofhomogenizer, duration of homogenization, proportions of monomers towater to protective colloids, method of dispersion used (once, twice ormore times, as a batch or continuously, with or without recirculation),speed of rotation of the homogenizer, etc.).

The precise polymerization conditions, particularly as regards the type,amount and metering of the emulsifier and other polymerizationauxiliaries, are preferably selected such that the resulting particlesof rubbers A obtained by emulsion polymerization have a mean particlesize (weight-average particle size d₅₀) usually from 50 to 500 andpreferably from 70 to 300 and more preferably from 80 to 140 nm. Therubbers A obtained by miniemulsion polymerization usually have particlesizes of from 50 to 500 nm (weight-average particle size d₅₀).Microemulsion polymerization produces particle sizes (weight-averageparticle sizes d₅₀) in the range of from 20 to 80 nm. The particle sizesstated always refer to the d₅₀ value (weight average, determined byanalytical ultracentrifuge measurements as described by W. Mächtle, S.Harding (Eds.), AUC in Biochemistry and Polymer Science, Cambridge,Royal Society of Chemistry UK 1992 pp. 1447-1475).

The method of microsuspension polymerization generally producesparticles having a size (weight-average particle size d₅₀) in the rangeof from 0.3 to 10 μm. The particle sizes can be determined by the methodof Fraunhofer diffraction (H. G. Barth, Modern Methods of Particle SizeAnalysis, Wiley, N.Y. 1984).

The monomers a) are polymerized conventionally up to a conversion ofusually at least 90% and preferably greater than 95%, based on themonomers used.

The rubber A dispersed in the aqueous phase is then agglomeratedaccording to the invention. There may be more than one, for example twoor more, rubbers present in the dispersion. This can be achieved e.g.,by mixing dispersions of different rubbers. Agglomeration is achieved bythe addition of a dispersion of the agglomerating polymer B and thebasic electrolyte.

In the present invention, B contains substantially no free acid groups,i.e., B contains, if at all, only free acid groups which might have comeabout through impurities or side reactions during manufacture of B.Examples of suitable agglomerating polymers are copolymers containingpolar comonomers. Suitable agglomerating polymers include copolymers ofC₁-C₁₂ alkyl acrylates or C₁-C₁₂ alkyl methacrylates and polarcomonomers such as acrylamide, methacrylamide, ethacrylamide,n-butylacrylamide or maleamide.

It is preferred to use copolymers of

b1) from 80 to 99.9% by weight of (C₁-C₄-alkyl) esters of acrylic acidand

b2) from 0.1 to 20% by weight and preferably from 0.1 to 10% by weightof acrylamides,

the sum of monomers b1) and b2) being 100% by weight. The monomers b1)used may be mixtures of various acrylates. Monomer b1) is preferablyethyl acrylate. Preferred monomers b2) include acrylamide,methacrylamide, N-methylolmethacrylamide or N-vinylpyrrolidone ormixtures of said compounds. B is very preferably a copolymer of from 92to 99% by weight of ethyl acrylate and from 1 to 8% by weight ofmethacrylamide. Preferred agglomerating polymers B include those havinga molecular weight (weight average M_(w)) of from 30,000 to 300,000g/mol.

The concentration of the agglomerating polymers in the dispersion usedfor agglomeration should generally be in the range from 3 to 60% byweight and preferably from 5 to 40% by weight. The agglomeratingdispersion may, if desired, comprise a mixture of, say, two or moredifferent agglomerating polymers. Preferably B is dispersed in anaqueous phase.

Agglomeration is usually carried out using from 0.1 to 5 and preferablyfrom 0.5 to 3 parts by weight of the agglomerating dispersion per 100parts by weight of the rubber, each based on solids.

The agglomeration is preferably carried out at a temperature of from 20to 120° C. and more preferably from 30 to 100° C. The addition of B cantake place all at once or in portions, continuously or according to afeed profile over a certain period of time. In a preferred embodiment,the addition of B is carried out in such a manner that 1/1 to 1/100 ofthe total amount of B are introduced per minute. The agglomerating timeis preferably from 1 minute to several hours, for example up to twohours, and more preferably from 10 to 60 minutes.

In accordance with the invention, suitable basic electrolytes includeorganic or inorganic hydroxides. Inorganic hydroxides are especiallysuitable. Monovalent basic electrolytes are preferred. Particularpreference is given to the use of lithium hydroxide, sodium hydroxide orpotassium hydroxide. In one preferred embodiment, KOH is used as basicelectrolyte. In another preferred embodiment, NaOH is used as basicelectrolyte. Additionally, however, mixtures of two or more basicelectrolytes can be used. This can be advantageous, for example, when itis desired to exert precise control over the growth of the rubberparticles. Thus it can be advantageous, for example, to use mixtures ofLiOH with KOH or mixtures of LiOH with NaOH. Using mixtures of KOH andNaOH is a further option and a further preferred embodiment.

Generally, the electrolytes are dissolved prior to being added. Thepreferred solvent is the aqueous phase. Preference is given to the useof dilute solutions, e.g., solutions with a concentration in the rangefrom 0.001 to 0.1, particularly in the range from 0.001 to 0.05, morepreferably less than 0.03, e.g., less than 0.025 g, of basic electrolyteper mL of solvent. The addition of the basic electrolytes can take placeprior to the addition of the agglomerating polymer, simultaneouslytherewith or separately or following the addition of B. An alternativepossibility is to premix the basic electrolytes in the dispersion of B.In a preferred embodiment, the addition of the basic electrolytes iscarried out prior to the addition of the agglomerating polymer. Usuallythe basic electrolyte is used in an amount ranging from 0.01 to 4,preferably from 0.05 to 2.5, particularly from 0.1 to 1.5% by weight,based on rubber A (as solids).

The pH during agglomeration is generally from 6 to 13. In a preferredembodiment it is from 8 to 13.

The agglomerated rubbers A produced by the process of the invention aresuitable for use as graft base for the synthesis of graft polymers (C).Theoretically, the rubbers can be grafted with a very wide variety ofunsaturated compounds. Appropriate compounds and methods are known tothe person skilled in the art. Preference is given to graft polymers Cwhich contain (based on C and solids)

c1) from 30 to 95, preferably from 40 to 90 and more preferably from 40to 85% by weight of graft base and

c2) from 5 to 70, preferably from 10 to 60, and more preferably from 15to 60% by weight of a graft component.

Preference is given to a graft component c2) comprising

c21) from 50 to 100, preferably from 60 to 100 and more preferably from65 to 100% by weight of a styrene compound of the general formula

in which R¹ and R² independently stand for hydrogen or C₁-C₈-alkyl,

c22) from 0 to 40%, preferably from 0 to 38% and more preferably from 0to 35% by weight of acrylonitrile or methacrylonitrile or a mixturethereof,

c23) from 0 to 40, preferably from 0 to 30 and more preferably from 0 to20% by weight of one or more further monoethylenically unsaturatedmonomers.

The graft component c2) can be produced in one or more process steps.The monomers c21), c22) and c23) may be added individually orintermixed. The ratio of the monomers in the mixture may be constant intime or follow a gradient. Alternatively, combinations of these methodscan be used.

For example, first of all styrene alone and then a mixture of styreneand acrylonitrile can be polymerized onto graft base c1).

If desired, however, other monomers c2) can be used, for example methylmethacrylate. Furthermore, component c2) may contain, at the expense ofmonomers c21) and c22), one or more other monoethylenically unsaturatedmonomers c23). As regards monomers c23), reference is made to theremarks concerning component a13).

Preferred graft components c2) are for example polystyrene andcopolymers of styrene and/or a-methylstyrene with one or more of theother monomers described under c22) and c23). Preference is given tomethyl methacrylate, N-phenylmaleimide, maleic anhydride andacrylonitrile and more preferably to methyl methacrylate andacrylonitrile.

As examples of preferred graft components c2) there may be mentioned:

c2-1: polystyrene

c2-2: copolymer of styrene and acrylonitrile,

c2-3: copolymer of α-methylstyrene and acrylonitrile,

c2-4: copolymers of styrene and methyl methacrylate.

The amount of styrene or α-methylstyrene, or the total amount of styreneand α-methylstyrene, is very preferably at least 40% by weight, based onc2).

The graft polymers can be used for the preparation of thermoplasticmolding compositions and are for this purpose mixed with one or moreother polymers. In this case the graft component c2) acts ascompatibility promoter between graft base c1) and the matrix polymerinto which the graft polymers C are embedded. Preferably, therefore,monomers c2) are the same as those of the matrix. If the matrix consistsentirely or predominantly of a poly(styrene-co-acrylonitrile) (SAN), thegraft component as well will usually entirely or predominantly consistof styrene and/or α-methylstyrene and acrylonitrile.

Graft component c2) is generally polymerized in emulsion in the presenceof the agglomerated rubber A. The process is usually carried out at from20 to 100° C. and preferably from 50 to 80° C. In a manner similar tothat described above regarding the preparation of the rubber, graftingcan take place as a batch process, a feed process or a continuousprocess.

The polymerization initiator used for the graft component can comprisethe same water-soluble compounds as employed during polymerization ofthe graft base. In the same way use can be made of oil-solubleinitiators or initiators that are soluble in the monomer, examples beingdialkyl peroxides such as dilauryl peroxide and dibenzyl peroxide, peresters such as tert-butyl perpivalate and tert-butyl peroxyneodecanoate,further diperoxyketals, peroxycarbonates and azo compounds such asazodiisobutyronitrile (azobisisobutyronitrile, AIBN) andazodiisovaleronitrile (ADVN). Furthermore, hydroperoxides, particularlycumene hydroperoxide, are suitable as polymerization initiators.

Details on how to carry out the grafting reaction in emulsion may befound, for example, in DE-A 24 27 960 and EP-A 62901.

The gross composition of the graft polymers C is not affected by thestated embodiments of the process.

Also suitable are graft polymers having a number of “soft” and “hard”stages, e.g., having the structure c1)-c2)-c1)-c2) or c2)-c1)-c2),particularly in the case of larger particles.

If grafting is accompanied by the formation of ungrafted polymers of themonomers c2), these amounts, which are usually below 10% by weight ofc2), are assigned to the mass of component C.

Graft copolymers C are, for the preparation of thermoplastic moldingcompositions (D), preferably blended with at least one matrix polymerand optionally other components. These are described below.

Examples of suitable matrix polymers d1) are amorphous polymers.

Examples thereof are SAN (styrene/acrylonitrile), AMSAN(α-methylstyrene/acrylonitrile), styrene/maleimide, SMSAN(styrene/maleic acid (anhydride)/acrylonitrile polymers or SMA(styrene/maleic anhydride).

Preferably, component d1) is a copolymer of

d11) from 60 to 100% by weight and preferably from 65 to 80% by weightof units of a vinylaromatic monomer, preferably styrene, a substitutedstyrene or a (meth)acrylate or a mixture thereof, particularly ofstyrene and/or α-methylstyrene,

d12)from 0 to 40% by weight and preferably from 20 to 35% by weight ofunits of an ethylenically unsaturated monomer, preferably acrylonitrileor methacrylonitrile or methyl methacrylate (MMA), particularlyacrylonitrile.

According to one embodiment of the invention it is composed of 60-99% byweight of vinylaromatic monomers and 1-40% by weight of at least one ofthe other monomers stated.

In one embodiment of the invention the component d1) used is a copolymerof styrene and/or α-methylstyrene with acrylonitrile. The acrylonitrilecontent in these copolymers is 0-40% by weight and preferably 20-35% byweight, based on the total weight of d1).

The thermoplastic molding compositions D can, furthermore, contain, asmatrix polymer, in addition to d1) or alone, preferably at least onepolymer selected from the group consisting of partially crystallinepolyamides, partially aromatic polyamides, polyesters, polyoxyalkylenes,polycarbonates, polyarylene sulfides and polyether ketones.Alternatively, mixtures of two or more of said polymers can be used. Ofcourse, it is possible to use mixtures of different individual polymers,e.g., mixtures of different polyamides, different polyesters ordifferent polycarbonates, as matrix polymers.

Suitable polymers d2) in the molding composition of the invention arepartially crystalline, preferably linear, polyamides such aspolyamide-6, polyamide-6,6, polyamide-4,6, polyamide-6,12 and partiallycrystalline copolyamides (d3) based on these components. Furthermore,partially crystalline polyamides can be used whose acid componentconsists completely or partially of adipic acid and/or terephthalic acidand/or isophthalic acid and/or suberic acid and/or sebacic acid and/orazelaic acid and/or dodecanedicarboxylic acid and/or acyclohexanedicarboxylic acid, and whose diamine component consistscompletely or partially of, in particular, m- and/or p-xylylenediamineand/or hexamethylenediamine and/or 2,2,4- and/or2,4,4-trimethylhexamethylenediamine and/or isophronediamine, and thecomposition of which is basically known from the prior art.

Additionally, the polymers d4) used can be polyesters, preferablyaromatic-aliphatic polyesters. Examples are polyalkylene terephthalates,based, for example, on ethylene glycol, 1,3-propanediol, 1,4-butanediol,1,6-hexanediol and 1,4-bishydroxymethylcyclohexane, and alsopolyalkylene naphthalates.

Furthermore, polymers d5) used can be polyoxyalkylenes, e.g.,polyoxymethylene.

Suitable polycarbonates d6) are known per se or can be obtained by knownmethods. Preference is given to polycarbonates based on diphenylcarbonate and bisphenols. The preferred bisphenol is2,2-di(4-hydroxyphenyl)propane, generally referred to, as below, asbisphenol A.

Instead of bisphenol A use can be made of other aromatic dihydroxycompounds, particularly 2,2-di(4-hydroxyphenyl)pentane,2,6-dihydroxynaphthalene, 4,4′-dihydroxydiphenyl sulfone,4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfide,4,4′-dihydroxydiphenylmethane, 1,1-di(4-hydroxyphenyl)ethane,4,4-dihydroxybiphenyl or dihydroxydiphenylcycloalkanes, preferablydihydroxydiphenylcyclohexanes or dihydroxylcyclopentanes, particularly1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and also mixtures ofthe aforementioned dihydroxy compounds.

Particularly preferred polycarbonates are those based on bisphenol A orbisphenol A together with up to 80 mol % of the aforementioned aromaticdihydroxy compounds.

Alternatively, copolycarbonates can be used; of particular interest arecopolycarbonates based on bisphenol A anddi(3,5-dimethyldihydroxyphenyl) sulfone, which are characterized by highheat distortion resistance.

Also suitable are polyarylene sulfides, particularly polyphenylenesulfide.

Furthermore, molding compositions D can contain, as a further component,additives E.

Preferred thermoplastic molding compositions contain, as component E,0-50% by weight, preferably 0-40% by weight and more preferably 0-30% byweight of fibrous or particulate fillers or mixtures thereof, based, ineach case, on the total molding composition.

If used, reinforcing agents such as carbon fibers and glass fibers areusually employed in amounts of 5-50% by weight based on the totalmolding composition.

The glass fibers used can be of glass type E, A or C and are preferablycoated with size and adhesion promoter. Their diameter is generally from6 to 20 μm. It is possible to use rovings or chopped strands (staplefibers) having a length of 1-10 μm and preferably 3-6 μm.

Furthermore, fillers or reinforcing materials, such as glass beads,mineral fibers, whiskers, aluminum oxide fibers, mica, quartz powder andwollastonite, can be added.

In addition, metal flakes, e.g., aluminum flakes, metal powders, metalfibers, metal-coated fillers, e.g., nickel-coated glass fibers, andother additives capable of shielding against electromagnetic waves maybe blended into molding compositions D. Furthermore, the moldingcompositions can be mixed with additional carbon fibers, carbon black,in particular conductive carbon black, or nickel-coated C fibers.

Molding compositions D can contain other additives as well. As examplesthereof there may be mentioned: dyes, pigments, colorants, antistaticagents, antioxidants, stabilizing agents for improving thermostability,increasing light stability, improving resistance to hydrolysis andresistance to chemicals, agents counteracting thermal decomposition and,in particular, lubricants or release agents, which are advantageous whenmanufacturing shaped articles or moldings or films. Metering of thesefurther additives can take place at any stage of the process for themanufacture of D, but preferably early on, in order to exploit thestabilizing action (or other specific effects) of the respectiveadditive at an early stage.

Suitable stabilizers are for example hindered phenols, but also vitaminE or compounds having an analogous structure, and butylated condensationproducts of p-cresol and dicyclopentadiene and also HALS stabilizers(Hindered Amine Light Stabilizers), benzophenones, resorcinols,salicylates and benzotriazoles. Other suitable compounds are e.g.,thiocarboxylates. Preference is given to C₆-C₂₀ fatty acid esters ofthiopropionic acid, stearyl and lauryl esters being particularlypreferred. Very special reference is given to the use of dilaurylthiodipropionate, distearyl thiodipropionate or mixtures thereof.Further additives are for example HALS absorbers, such asbis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, or UV absorbers such as2H-benzotriazol-2-yl-4-methylphenol. Such additives are usually employedin amounts of up to 2% by weight (based on the total mixture).

Suitable lubricants and mold release agents are stearic acids, stearylalcohol, stearates, amide waxes (bis-stearylamide), polyolefin waxes or,generally, higher fatty acids, derivatives thereof and mixtures of suchfatty acids containing from 12 to 30 carbons. The amounts of theseadditives are in the range from 0.05 to 5% by weight.

In addition, silicone oils, oligomeric isobutylene or similar materialsare suitable for use as additives. If used, the usual concentrationsthereof are from 0.001 to 5% by weight. Pigments, dyes, colorbrighteners, such as ultramarine blue, phthalocyanines, titanium(IV)oxide, cadmium sulfides, derivatives of perylenetetracarboxylic acid arealso useful.

Processing assistants and stabilizers such as UV stabilizers, lubricantsand antistatic agents, if used, are usually employed in amounts of from0.01 to 5% by weight, based on the total molding composition.

Mixing of graft polymers C with the other constituents to producemolding compositions D may be carried out by any known method and in anydesired manner. However, blending of the components is preferablycarried out by coextruding, kneading or roll-milling the components attemperatures of, say, from 180 to 400° C., the components having beenpreviously isolated if necessary from the solution or aqueous dispersionobtained in the polymerization. The products of the graftcopolymerization (component C), obtained in aqueous dispersion, can forexample be only partially dewatered and mixed as moist crumbs with thematrix polymers, in which case drying of the graft copolymers iscompleted during the mixing operation.

The molding compositions can be processed to shaped articles, films orfibers.

According to one embodiment of the invention, these can be prepared frommolding compositions D by known methods of processing thermoplastics. Inparticular, production may be effected by thermoforming, extruding,injection molding, calendering, blow molding, pressing, pressuresintering, deep drawing or sintering, preferably by injection molding.

The molded articles prepared from molding compositions D arecharacterized by relatively high impact strengths. In addition, theyhave an improved surface quality, particularly greater luster.

The invention is illustrated below with reference to the followingexamples.

EXAMPLES

Test Methods

Charpy Impact Strength (ak [kJ/m²])

Tests were carried out on specimens (80×10×4 mm, prepared according toISO 294 in a family mold at a mass temperature of 240° C. and a moldtemperature of 50° C.) at 23° C. and −40° C. according to ISO 179-2/leA(F).

Puncture Resistance (Multiaxial Toughness) [Nm]

Tests were carried out according to ISO 6603-2 on plates (60×60×2 mm,prepared according to ISO 294 in a family mold at a mass temperature of240° C. and a mold temperature of 50° C.)

Flowability (MVR [ml/10′])

Tests were carried out according to ISO 1133 B on the polymer melt at220° C. under a load of 10 kg

Elasticity (Modulus of Elasticity [MPa])

Tests were carried out according to ISO 527-2/1A/50 on specimens(prepared according to ISO 294 at a mass temperature of 250° C. and amold temperature of 60° C.)

Amount of Coagulum

The amount of coagulum relative to the graft rubber is determined afterfiltration through a sieve having a mesh size of about 1 mm, dried at80° C. under nitrogen (200 mbar) for 17 hours.

Particle Size

The mean particle size d stated is the weight average of the particlesize, as determined with an analytical ultracentrifuge following themethod of W. Mächtle, S. Harding (Eds.), AUC in Biochemistry and PolymerScience, Royal Society of Chemistry Cambridge, UK 1992 pp. 1447-1475.The ultracentrifuge readings give the integral mass distribution of theparticle diameter in a sample. This makes it possible to determine whatpercentage by weight of the particles have a diameter equal to orsmaller than a specific size.

The weight-average particle diameter d₅₀ indicates that particlediameter at which 50% by weight of all particles have a larger particlediameter and 50% by weight have a smaller particle diameter.

Swell Index and Gel Content [%]

A film was prepared from the aqueous dispersion of the graft base byevaporating the water. To 0.2 g of this film there were added 50 g oftoluene. After a period of 24 hours the toluene was removed from theswollen sample by filtration with suction and the sample was weighed.After drying in vacuo at 110° C. over a period of 16 hours, the samplewas reweighed. The indicators were calculated as follows:$\begin{matrix}{{{Swell}\quad {index}\quad {SI}} = \frac{{{mass}\quad {of}\quad {swollen}},{{suction}\text{-}{filtered}\quad {specimen}}}{{mass}\quad {of}\quad {vacuum}\text{-}{dried}\quad {specimen}}} \\{{{Gel}\quad {content}} = {{\frac{{mass}\quad {of}\quad {vacuum}\text{-}{dried}\quad {specimen}}{{initial}\quad {mass}\quad {of}\quad {unswollen}\quad {specimen}} \cdot 100}\quad \%}}\end{matrix}$

Butadiene Rubber (A₁ to A₅)

Synthesis of the butadiene rubber (A₁ to A₅) took place by emulsionpolymerization by the feed process. As comonomer 10% by weight ofstyrene were used.

The butadiene rubbers had the following properties:

Rubber Swell index Gel content [%] d₅₀ [nm] A₁ 19 77 109 A₂ 28 74 100 A₃17 86 116 A₄ 22 76 104 A₅ 28 72 106

Experiment a (for Comparison)

To 60.47 kg of a dispersion of A₁ in water (solids content 43% byweight) there were added, at 55° C., 6.5 kg of a dispersion of copolymerB₁ (solids content 10% by weight, composition of B₁: 95.5% of ethylacrylate and 4.5% of methacrylamide (MAM)).

To the resulting dispersion of the agglomerated rubber A₁ an emulsifierwas added. There were then added 0.98 kg of acrylonitrile (AN), 2.52 kgof styrene (S) and tert-dodecyl mercaptan (regulator). The initiatorsystem used was one based on cumene hydroperoxide and dextrose andpolymerization was carried out at a temperature in the range from about60 to about 70° C. There were then added a further 2.94 kg ofacrylonitrile, 7.56 kg of styrene and regulator, emulsifier andinitiator. On completion of the polymerization reaction 0.05% ofsilicone oil and 0.6% of a stabilizer mixture, based, in each case, onthe total solids, were added and the mixture was allowed to cool down.

The dispersion was precipitated by means of magnesium sulfate solution.The resulting graft rubber C_(V1) was isolated and processed withpoly(styrene-co-acrylonitrile) (SAN) having an acrylonitrile content of24% by weight, by extrusion, to form a molding composition D_(V1) havinga content of 29% by weight of C_(V1).

Experiment b (Invention)

Experiment a was repeated except that 0.27% by weight of KOH, based onthe solids content of the dispersion of A₂, was added to the dispersionof the rubber prior to the addition of copolymer B₁.

The resulting dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C₁ was isolated and processed withSAN having an acrylonitrile content of 24% by weight, by extrusion, toform a molding composition D₁ having a content of 29% by weight of C₁.

Experiment c (Invention)

To 4727.3 g of the dispersion of A₃ in water (solids content 44% byweight there were added 11.2 g of a 10% by weight strength KOH solution.The fraction of KOH solids was 0.054% by weight based on the solidscontent of the dispersion of A₃. The mixture was then heated to 55° C. A10% by weight strength dispersion of copolymer B₁ was then added, theadded amount of solids of this agglomerating dispersion being 2.5% ofthe solids content of the polybutadiene dispersion.

14.4 g of a 10% by weight strength KOH solution, emulsifier and waterwere then added and stirring was continued for a few minutes.

78.4 g of acrylonitrile, 201.6 g of styrene and tert-dodecyl mercaptanwere then added. The reaction mixture was heated and an initiator systembased on cumene hydroperoxide and dextrose was added thereto, and themixture was polymerized at about 70° C. A further 235.2 g ofacrylonitrile, 604.8 kg of styrene and regulator and also emulsifier,initiator and water and 3.84 g of a 10% by weight strength solution ofKOH in water were then added. On completion of the polymerizationreaction 0.05% of silicone oil and 0.6% of a stabilizer mixture, based,in each case, on the total solids content, were added and the mixturewas allowed to cool down.

The dispersion was precipitated by means of magnesium sulfate solution.The resulting graft rubber C₂ was isolated and processed with SAN havingan acrylonitrile content of 28% by weight, by extrusion, to form amolding composition D₂ having a content of 29% by weight of C₂.

Experiment d (Invention)

Experiment c was repeated except that 0.11% by weight of KOH based onthe solids content of the dispersion of A₃ was added to the dispersionof the rubber prior to addition of copolymer B₁.

The resulting dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C₃ was isolated and processed withSAN having an acrylonitrile content of 28% by weight, by extrusion, toform a molding composition D₃ having a content of 29% by weight of C₃.

Experiment e (Invention)

Experiment c was repeated except that 0.27% by weight of KOH, based onthe solids content of the dispersion of A₃, was added to the dispersionof the rubber prior to the addition of copolymer B₁.

The dispersion was precipitated by means of magnesium sulfate solution.The resulting graft rubber C₄ was isolated and processed with SAN havingan acrylonitrile content of 28% by weight, by extrusion, to form amolding composition D₄ having a content of 29% by weight of C₄.

Experiment f (For Comparison)

To 4952.4 g of a dispersion A₂ (solids content 42% by weight) in waterthere was added, at about 70° C., a 10% by weight strength agglomeratingdispersion of B₂ (composition of B₂: 96% of ethyl acrylate and 4% ofMAM), the added amount of solid material of the agglomerating dispersionbeing 4% of the solids content of the polybutadiene dispersion.

Following agglomeration, emulsifier and initiator (potassium persulfate)were added. 46.67 g of acrylonitrile, 140 g of styrene and regulatorwere then added. A mixture of 233.33 g of acrylonitrile, 700 g ofstyrene and regulator was then added over a period of 190 minutes, thetemperature being raised to 77° C. after over half of the time. Oncompletion of the addition of monomer, initiator was again added and thepolymerization was continued.

To the dispersion there were added 0.02% by weight of silicone oil and0.2% by weight of a stabilizer, based, in each case, on the total solidscontent, and the mixture was cooled.

The dispersion was precipitated by means of magnesium sulfate solution.The resulting graft rubber C_(V2) was isolated and processed with SANhaving an acrylonitrile content of 24% by weight, by extrusion, to forma molding composition D_(V2) having a content of 29% by weight ofC_(V2).

Experiment g (Invention)

Experiment f was repeated except that additionally 0.54% of KOH, basedon the solids content of the polybutadiene dispersion, was added.

The dispersion was precipitated by means of magnesium sulfate solution.The resulting graft rubber C₅ was isolated and processed with SAN havingan acrylonitrile content of 24% by weight, by extrusion, to form an ABSmolding composition D₅ having a content of 29% by weight of C₅.

Experiment h (Invention)

Experiment f was repeated except that additionally 0.27% of KOH, basedon the solids content of the polybutadiene dispersion, was added. Theadded amount of solid material in the agglomerating dispersion was 2.5%of the solids content of the polybutadiene dispersion.

The dispersion was precipitated by means of magnesium sulfate solution.The resulting graft rubber C₆ was isolated and processed with SAN havingan acrylonitrile content of 24% by weight, by extrusion, to form amolding composition D₆ having a content of 29% by weight of C₆.

Experiment i (Invention)

Experiment f was repeated except that additionally 0.27% of KOH, basedon the solids content of the polybutadiene dispersion, was added. Theadded amount of solid material in the agglomerating dispersion of B₃(composition of B₃: 94% of ethyl acrylate and 6% of MAM) was 2.5% of thesolids content of the polybutadiene dispersion.

The dispersion was precipitated by means of magnesium sulfate solution.The resulting graft rubber C₇ was isolated and processed with SAN havingan acrylonitrile content of 24% by weight, by extrusion, to form amolding composition D₇ having a content of 29% by weight of C₇.

Experiment j (Invention)

To 5580 g of a dispersion A₄ (solids content 40% by weight) in waterthere was added, at about 70° C., 0.37% by weight strength KOH, based onthe solids content of the dispersion of A₄. Then a 10% by weightstrength agglomerating dispersion of B₂ (composition of B₂: 95.5% ofethyl acrylate and 4.5% of MAM), the added amount of solid material ofthe agglomerating dispersion being 1.5% of the solids content of thepolybutadiene dispersion.

Following agglomeration, emulsifier and initiator (potassium persulfate)were added. 47.9 g of acrylonitrile and 180 g of styrene were thenadded. A mixture of 239 g of acrylonitrile and 900 g of styrene was thenadded over a period of 190 minutes, the temperature being raised to 77°C. after over half of the time. On completion of the addition ofmonomer, initiator was again added and the polymerization was continued.

To the dispersion there was added 0.2% by weight of a stabilizer, basedon the total solids content, and the mixture was cooled.

The dispersion was precipitated by means of magnesium sulfate solution.The resulting graft rubber C₈ was isolated and processed with SAN havingan acrylonitrile content of 24% by weight, by extrusion, to form amolding composition D₈ having a content of 29% by weight of C₈.

Experiment k (Invention and for Comparison)

Experiment j was repeated except that additionally the type and amountof electrolyte indicated in Table 4, based on the solids content of thepolybutadiene dispersion, were added.

The dispersion was precipitated by means of magnesium sulfate solution.The resulting graft rubber C₉ to C₁₁ and C_(v3) to C_(v7) was isolatedand processed with SAN having an acrylonitrile content of 24% by weight,by extrusion, to form an ABS molding composition D₉ to D₁₁ and D_(v3) toD_(v7) having a content of 29% by weight of C₉ to C₁₁ and C_(v3) toC_(v7), respectively

Experiment l (Invention and For Comparison)

The procedure of experiment j was repeated. The rubber used was therubber A₅.

The agglomerating polymer used was the copolymer B₁. For comparison, thecopolymers B_(v1) to B_(v4) were used, containing acrylic acid ormethacrylic acid groups and being prepared as follows:

Preparation of B₁

333 g of ethyl acrylate, water, emulsifier and potassium persulfate wereintroduced as an initial charge, adjusted to a pH of from 8 to 9, andstirred at 80° C. Then a further 2681 g of ethyl acrylate, 126 g of methacrylamide, emulsifier, water and free-radical initiator were meteredin. After about 4½ hours, the reaction mixture was cooled to roomtemperature and the resulting dispersion was diluted in water to 10% byweight.

Preparation of B_(v1)

The procedure described under B₁ was repeated but initially introducing360 g of ethyl acrylate and metering in 2905 g of ethyl acrylate and,instead of methyl acrylate, 136 g of acrylic acid.

After the reaction mixture had been cooled to room temperature, thedispersion was diluted to 10% by weight with an aqueous KOH solutioncontaining an amount of KOH equimolar with the acrylic acid.

Preparation of B_(v2)

The procedure described under B_(v1) was repeated but using methacrylicacid instead of acrylic acid.

Preparation of B_(v3)

The procedure described under B_(v1) was repeated except that thedispersion was diluted to 10% by weight with water instead of aqueousKOH solution.

Preparation of B_(v4)

The procedure described under B_(v2) was repeated except that thedispersion was diluted to 10% by weight with water instead of aqueousKOH solution.

When using B_(v3) and B_(v4), an equimolar amount of KOH with respect toacrylic acid or methacrylic acid, respectively, was added in addition tothe amount of KOH stated in Table 5.

The results of the experiments are compiled in Table 5.

TABLE 1 Comparison Invention Experiment a b Rubber A A₁ A₂ Ratio AN/S inC 28/72 (C_(v1)) 28/72 (C₁) Conc. of MAM in B₁ [%] 4.5 4.5 Amount of B₁[%] 2.5 2.5 Electrolyte none KOH Amount of electrolyte [%] 0.27Initiator Redox Redox pH (following grafting) 9.58 9.92 Particle size ofC 238 369 d₅₀ [nm] Conc. of AN in SAN [%] 24 24 ak (23° C.) [kJ/m²] 13.619.7 ak (−40° C.) [kJ/m²] 4 9.1 Puncture resistance [Nm] 23.6 21.2 MVR(220/10) [cm³/10 min] 16.4 17.7 E modulus [MPa] 2080 2040 Coagulum [%]1.2 0.3

TABLE 2 Invention Invention Invention Experiment c d e Rubber A A₃ A₃ A₃Ratio of AN/S in C 28/72 (C₂) 28/72 (C₃) 28/72 (C₄) Conc. of MAM [%] inB 4.5 4.5 4.5 Amount of B [%] 2.5 2.5 2.5 Electrolyte KOH KOH KOH Amountof electrolyte [%] 0.054 0.11 0.27 Initiator Redox Redox Redox pH(following grafting) 9.82 9.97 10.28 Particle size of C 151 267 325 d₅₀[nm] Conc. of AN in SAN [%] 28 28 28 ak (23° C.) [kJ/m²] 22.2 20.7 21.3ak (−40° C.) [kJ/m²] 7.6 7.6 7.8 Puncture resistance [Nm] 27.8 25.9 26.4MVR (220/10) [cm³/10 min] 20.5 19.5 18.7 E modulus [MPa] 2230 2210 2170Coagulum [%] 0.15 0.15 0.075

TABLE 3 Compari- Inven- Inven- Inven- son tion tion tion Experiment f gh i Rubber A A₂ A₂ A₂ A₂ Ratio of AN/S in C 25/75 25/75 25/75 25/75(C_(v2)) (C₅) (C₆) (C₇) Conc.of MAM [%] in B 4 4 4 6 Amount of B [%] 4 42.5 2.5 Electrolyte none KOH KOH KOH Amount of electrolyte [%] 0.54 0.270.27 Initiator KPS KPS KPS KPS Particle size of C 207 350 358 362 d₅₀[nm] pH (following grafting) 8.87 10.58 10.23 10.10 Conc. of AN in SAN[%] 24 24 24 24 ak (23° C.) [kJ/m²] 11.1 25,.3 25.2 19 ak (−40° C.)[kJ/m²] 5.8 7.5 8.3 7.3 Puncture resistance [Nm] 5.7 12.3 29.4 21.4 MVR(220/10) [cm³/10 min] 23.7 21.1 20.2 23.5 E modulus [MPa] 2405 2367 22782384 Coagulum [%] 0.06 0.08 0.02 0.06

TABLE 4 Invention Invention Comparison Comparison Comparison InventionInvention Comparison Comparison Experiment j k k k k k k k k Rubber A A₄A₄ A₄ A₄ A₄ A₄ A₄ A₄ A₄ Ratio of AK/S in C 21/79 (C₈) 21/79 (C₉) 21/79(C_(v3)) 21/79 (C_(v4)) 21/79 (C_(v5)) 21/79 (C₁₀) 21/79 (C₁₁) 21/79(C_(v6)) 21/79 (C_(v7)) Conc. of MAM [%] in B 4.5 4.5 4.5 4.5 4.5 4.54.5 4.5 4.5 Amount [%] in B 1.5 1.5 1.5 1.5 1.5 2.5 2.5 2.5 2.5Electrolyte KOH NaOH NaHCO₃ KCl K₂SO₄ KOH NaOH NaHCO₃ K₂SO₄ Amount ofelectrolyte 0.37 0.2638 0.5542 0.4906 0.5734 0.27 0.1925 0.4044 0.4193[%] Initiator KPS KPS KPS KPS KPS KPS KPS KPS KPS pH (followinggrafting) 11.26 11.58 8.84 10.61 10.56 PSD of C 140 141 135 324 299 d₅₀[nm]  D50 [nm] Conc. of AN in SAN [%] 24 24 24 24 24 PB content (sec.)[%] 29.1 29.2 28.3 28.3 29.5 ak 23° C. [kJ/m²] 23.3 23 23.1 21.4 22.3 ak−40° C. [kJ/m²] 7.2 7.6 8.1 7.8 7.9 Puncture resistance 23 ° C. [Nm] MVR220/10 16.3 16.4 17.1 16.8 15.9 [ml/10 min] Vicat B50 [° C.] 98.3 98.398.5 98.4 98.2 Coagulum (t)  grams 3.6 12.35 137.4 0.8 0.8 Coagulum (%)0.11 0.39 4.29 fully fully 0.03 0.03 coagulated fully coagulatedcoagulated coagulated

TABLE 5 Inven- Com- Com- Com- Com- tion parison parison parison parisonExperiment l l l l l Rubber A A₅ A₅ A₅ A₅ A₅ Ratio of AN/S in C 21/7921/79 21/79 21/79 21/79 (C₁₂) (C_(V8)) (C_(V9)) (C_(V10)) (C_(V11)) B B₁B_(v1) B_(v2) B_(v3) B_(v4) Amount [%] in B 1.5 1.5 1.5 1.5 1.5Electrolyte KOH KOH KOH KOH KOH Amount of electrolyte 0.27 0.27 0.270.27 0.27 [%] Initiator KPS KPS KPS KPS KPS pH (following grafting)10.94 11.4 10.93 10.77 10.86 PSD of C d₅₀ [nm]  D50 [nm] n.g. n.g. n.g.n.g. n.g. Conc. of AN in SAN [%] 24 24 24 24 24 PB content (sec.) [%]28.3 28.5 28.9 28.2 28.3 ak 23° C. [kJ/m²] 25.5 25.1 25.5 25.2 25.1 ak−40° C. [kJ/m^(2]) 5.5 5.5 5.6 5.3 5.4 Puncture resistance 19.3 13.918.3 18.2 16.0 23° C. [Nm] MVR 220/10 20.1 19.4 18.1 20.9 20.1 [ml/10min] Vicat B50 [° C.] 96.3 96.2 95.7 95.9 95.8 Coagulum (t)  grams 1.742.2 9.2 39.1 12.1 Coagulum (%) 0.05 1.32 0.29 1.22 0.38 n.g.: notgauged

What is claimed is:
 1. A process for the agglomeration of at least onerubber (A), dispersed in an aqueous phase, by the addition of adispersion of at least one agglomerating polymer (B) in aqueous phase,wherein the agglomerating polymer (B) used is a copolymer of at leastone C₁-C₁₂-alkyl acrylate or C₁-C₁₂-alkyl methacrylate or a mixturethereof and at least one acrylamide or maleamide or a mixture thereof,which copolymer is substantially free of acid groups, and theagglomeration is carried out in the presence of at least one basicelectrolyte comprising an organic or inorganic hydroxide.
 2. A processas claimed in claim 1, wherein the agglomerating polymer (B) used is acopolymer of (based on B): b1) from 80 to 99.9% by weight of at leastone (C₁-C₄ alkyl)ester of acrylic acid and b2) from 0.1 to 20% by weightof acrylamide.
 3. A process as claimed in claim 1, wherein the basicelectrolyte used is KOH.
 4. A process as claimed in any of claim 1,wherein the rubber (A) used is a diene rubber of (based on A): a1) from50 to 100% by weight of at least one diene having conjugated doublebonds and a2) from 0 to 50% by weight of one or more othermonoethylenically unsaturated monomers.
 5. A process as claimed in claim1, wherein the basic electrolyte is used in an amount of from 0.01 to1.5% by weight based on (A).
 6. A graft polymer (C) containing (based onC): c1) from 30 to 95% by weight of rubber (A) agglomerated by theprocess as claimed in claim 1 and c2) from 5 to 70% by weight of a graftbase.
 7. A thermoplastic molding composition (D) comprising a graftpolymer (C) as claimed in claim 6.